An ongoing effort to reduce drag in vehicular structures is of great importance as fuel economy becomes an increasingly large consideration in vehicular design. As the drag of a vehicle increases, the amount of fuel needed to move the vehicle also increases due to the greater energy required to overcome the drag. For instance, it has been stated that for a vehicle traveling at 70 mph, about 65% of the total fuel consumption of the vehicle's engine is used to overcome drag. Therefore, even a small reduction in the drag experienced by a vehicle traveling at highway speeds can result in a significant improvement in fuel economy.
For instance, heavy-duty vehicles such as tractor-trailers (also known as semi tractors, tractors, class 8 long haul trucks, transfer trucks, 18-wheelers, semis, etc.) have a tall and wide box-shaped profile that creates a significant amount of drag compared to other common vehicles on the road such as cars and light trucks. For instance, Table I lists common drag coefficients of road vehicles.
TABLE IType of VehicleDrag Coefficient (Cd)Low Drag Production Car.26Typical Sedan .3-.35Sport Utility Vehicle.4-.5Pick-up Truck.4-.5Conventional Class 8 long haul tractor trailers.59-.63
In addition, such vehicles are generally equipped with large side mirror assemblies that extend outboard of the vehicle body structure to allow the driver to view rearward of the side mirror assembly. Although such side mirror assemblies are generally streamlined to the extent possible, because they increase the lateral profile of the vehicle, they nevertheless increase the drag on the vehicle with a corresponding reduction in fuel economy.
Thus, a need exists for improved aerodynamic mirror housings that are designed to provide drag reduction. Methods relating to the utilization of such mirror housings would also be beneficial. Retrofit kits for incorporating such mirror housings into vehicles would also be beneficial.